As a note, this is a somewhat older model semiPro Nikon dSLR. Its sensor won't be as new as some, but it will make up for it in usability and build quality. Noteably, it has a built-in focus motor, so it can focus the older (screwdriver) autofocus lenses. This isn't available on the d5XXX or x3XXX.
Personally, I'd pass and pick up a Pentax K30 instead at $533 (or a version with a kit lens). It will have significantly better image quality, though a smaller lens selection and worse flash system. I think most people considering a discount dSLR will be better served with this than a d90. If you're thinking about the really expensive (awesome) lenses available for Nikon, you're probably willing to buy the more expensive, newer bodies.
http://www.amazon.com/Pentax-K-30-We...dp/B0082OJ33Q/